The invention relates to apparatus for obtaining subsurface measurements.
Subsurface formation logs contain data related to one or more properties of a formation as a function of depth. A formation log is typically recorded as a logging tool traverses a borehole penetrating a formation of interest. The logging tool may be conveyed in a number of ways, e.g., on cable, on drill pipe, or on coiled tubing. For operational efficiency, it is common to include a combination of logging tools in a single logging run. One example of a combination of logging tools is a triple-combo tool, which measures formation density, porosity, deep and/or intermediate and/or shallow resistivity, natural gamma radiation, and borehole size in a single logging run. The standard triple-combo tool uses a separate tool to measure each type of formation property. While the individual tools are very modular, a tool string assembled from these modular tools is long, typically about 90 ft (27.4 m), and time consuming to setup and run into and out of the borehole.
Operating cost and equipment cost contribute to the cost of logging. Both may be reduced by making tools smaller and simpler. Smaller and lighter tools are easier to transport, setup, and operate. Simpler tools are cheaper to build. Integrating measurements and adopting novel approaches to implementing measurements can reduce tool size and complexity. Even a highly integrated tool can be broken down into several sections to optimize transport and handling. However, depending on the degree of integration, there may not be a one-to-one relationship between measurements and sections. Schlumberger offers an integrated wireline logging tool under the trade name Platform Express™ that is about half the length of the standard triple-combo tool. The integrated wireline logging tool includes an integrated gamma-ray and neutron sonde, a high-resolution mechanical sonde with associated electronics cartridge and pad-mounted measurements, and a high-resolution azimuthal laterolog sonde or array induction imager tool.